Turbo occasionally only giving half boost on my stock 02
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This is a discussion on Turbo occasionally only giving half boost on my stock 02 within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; My stock 02 WRX will at random go to about half boost, .5 bar on the gauge.. and it's slow, ...

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    Turbo occasionally only giving half boost on my stock 02

    My stock 02 WRX will at random go to about half boost, .5 bar on the gauge.. and it's slow, so it's not just a gauge malfunction. To fix it I have to disconnect the battery, then all is well for a few days. I changed the Boost control solenoid, but no luck. Any ideas??

    Thanks, Bill

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    Registered User teflon_jones's Avatar
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    Mileage? Mods? When did this start happening / how long has it been an issue? Did you do anything specific before it started like some sort of service service, change any parts, etc? Does it always happen once it starts that few days after reconnecting the battery, or is it intermittent?
    Scott
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    Totally stock, 150K miles. It's been doing this for the last year or so off and on. No changes at all to the car, it just started boosting at .5 bar one day, then I discovered that if I disconnected the battery it would fix it, boost was restored to 1 bar like normal. After a few days though it will start doing it again and the only fix is doing the battery thing.

    Quote Originally Posted by teflon_jones View Post
    Mileage? Mods? When did this start happening / how long has it been an issue? Did you do anything specific before it started like some sort of service service, change any parts, etc? Does it always happen once it starts that few days after reconnecting the battery, or is it intermittent?

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by Bill Meyer
    Totally stock, 150K miles. It's been doing this for the last year or so off and on. No changes at all to the car, it just started boosting at .5 bar one day, then I discovered that if I disconnected the battery it would fix it, boost was restored to 1 bar like normal. After a few days though it will start doing it again and the only fix is doing the battery thing.
    That means the car is likely going into limp mode. You shouldn't keep doing the battery "fix".
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    Quote Originally Posted by EJ257 View Post
    That means the car is likely going into limp mode. You shouldn't keep doing the battery "fix".
    Interesting, didn't know these had a "limp mode". Any ideas what some possible causes might be? The engine runs perfect otherwise, no check engine light or anything.

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    Knock is what usually causes limp mode. If you're stock it could just be a bad tank of gas. Regardless I'd have it checked by a reputable subaru shop ASAP.

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    Moderator Donkey's Avatar
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    Are you using 91- 93 octane?
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    91 is about all I can find around here, but I've been using that the entire time I've owned the car, 5+years and over 100K miles. This has been happening on and off the last year.

    Quote Originally Posted by Donkey View Post
    Are you using 91- 93 octane?

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    Admiral Ackbar the 1st mycologist's Avatar
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    Would limp mode throw a CEL?

    (still proceed with checking the tune)
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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    Registered User cjm1991's Avatar
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    If it's not throwing SES light, it's probably not a sensor. Going into limp mode could be caused by ping/knock, possibly dirty maf or filter, could have a boost leak or cracked hose somewhere. Did the gas station you use switch up something on you recently? Id try a new station if you haven't and see if that helps. Anything spark/afr gets reset when you reset the ecu. Its got something to do with air or fuel I'm guessing.. Sorry I couldn't help more.
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    Registered User poly_poly-man's Avatar
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    Quote Originally Posted by mycologist View Post
    Would limp mode throw a CEL?

    (still proceed with checking the tune)
    not if you got stuck in limp by an IAM lower than threshold.
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    No change in stations that I'm aware of, and since it's been doing it for about a year I doubt it's bad gas. I did change the plugs today and they looked pretty worn, It's probably been 75K since I last changed them so they were waaay over due. Changed the filter too so I'll give it a few days and see if the plugs fixed it.

    Quote Originally Posted by cjm1991 View Post
    If it's not throwing SES light, it's probably not a sensor. Going into limp mode could be caused by ping/knock, possibly dirty maf or filter, could have a boost leak or cracked hose somewhere. Did the gas station you use switch up something on you recently? Id try a new station if you haven't and see if that helps. Anything spark/afr gets reset when you reset the ecu. Its got something to do with air or fuel I'm guessing.. Sorry I couldn't help more.

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    Admiral Ackbar the 1st mycologist's Avatar
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    Clean your MAF per the instructions thread (note the sensor wire is up inside), reinstall facing the correct direction and tighten down all of the clamps on the intake tract leading to the turbo.

    If I were you I'd just get a cable to log it & check for CELs (which you could also use to flash stage I if you clear the problem).
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

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    Update.. New plugs didn't fix it. No CEL's on this car, ever for that matter, even cleaned the MAF as well. Had full boost half the day today, then back to limp mode. Guess I need to find a good place to take it, really scared to go to the dealer and have them start a wild goose chase on my dime though..

    Thanks for the suggestions so far!

    Quote Originally Posted by mycologist View Post
    Clean your MAF per the instructions thread (note the sensor wire is up inside), reinstall facing the correct direction and tighten down all of the clamps on the intake tract leading to the turbo.

    If I were you I'd just get a cable to log it & check for CELs (which you could also use to flash stage I if you clear the problem).

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    Did you check for boost leaks?

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